Mastering Blockchain Programming with Solidity

Avoid initial values in the field declaration

In contracts, you can assign initial values to the state variable:

contract MyContract {    uint256 public tokensToMint = 1000000;}

As we know, in normal contracts, the tokensToMint variable will be initialized with the previously given value. However, when writing upgradable contracts using zos, you should not define initial values for the state variables in the contract. These values must be set in the initialize() function, as follows:

contract MyContract is Initializable {    uint256 public tokensToMint;    function initialize() initializer public {        tokensToMint = 1000000;    }}

If these variables are not initialized in the initialize() function, then they will not be set.